The fact that these greenhouses used to grow ornamental species, fruit and crops are made of very transparent material such as polyethylene film, glass, etc, thus letting sunlight in them almost completely raises the inner temperatures at daytime, even more during summer, resulting in great losses of crops.
This permanently urges the producers to find an efficient and economical way to ventilate.
The way to let air in is through lateral and zenithal openings, the latter being the most effective one, as it allows the free convection of warm air which remains in the upper part of the greenhouse, letting it out as a chimney does.
Up to now, all the buildings which use this type of ventilation are very expensive, not affordable to many producers, and in some cases they are replaced by big electric air extractors, which as it is known, consume a lot of energy.
This device allows you to build a compact, plain, economical and efficient system for any kind of structure.
All greenhouses have parabolic, equilateral, hacksaw teeth and A-sloped roofs, which do not let the rolling devices known so far work upon them, as they only work rolling curtains vertically and they always slide on a straight guide, which leads them and lets them get the application points from the reaction forces of the torque, which is needed for rolling.
The stroke limits used up to now, are external keys or internal mechanisms based on gearing revolution counters, coil clutches, all these being difficult to be kept up, as this sort of plant growth is well known for the use of great moisture, heat and corrosive chemical compounds, which usually causes faults.